Pneumatic tool with as-cast air signal passage

ABSTRACT

A fastener driving device includes a housing containing a chamber for storing compressed air a cylinder structure disposed within the housing, a piston movably disposed within the cylinder, a driver connected to the piston, a main valve cooperable with the cylinder structure and movable between an open position and a closed position. The main valve in its open position allows air to move the piston through a drive stroke. The fastener driving device also includes a trigger valve operable between first and second positions. The trigger valve in its first position communicates air pressure from the chamber to the main valve through a signal passageway so as to retain the main valve in a closed position. The trigger valve in its second position allows the air to be exhausted to atmosphere through the signal passageway to permit the main valve to open. The cylinder and the signal passageway comprise an integrally molded structure.

This application is a divisional application of U.S. patent applicationSer. No. 10/406,579, filed Apr. 4, 2003, and claims priority to U.S.Provisional Application Nos. 60/369,802, 60/369,882, and 60/369,884, allfiled on Apr. 5, 2002. The entire contents of all of these applicationsare incorporated herein by reference.

BACKGROUND

1. Field of Invention

This invention relates to fastener driving devices and, moreparticularly, to fastener driving devices of the portable type.

2. Discussion of Related Art

Fastener driving tools for driving fasteners such as nails, staples orthe like are commonly used in industry and commerce. The fasteners aregenerally supplied from a collated strip or stick of fasteners disposedin a magazine coupled to a nose-piece portion of the fastener drivingtool. The fastener driving tool also comprises a housing to storecompressed air provided from an external source, and a cylinder isdisposed within the housing. A piston is slidably disposed in thecylinder and a driver is connected to the piston. A main valve can beopened above the cylinder to provide pressurized air to the pistonoperating the driver. A trigger valve is also provided and sends apneumatic signal to operate the main valve.

The pneumatic signal is routed from the trigger valve to the main valvevia an air passage. Conventional tools typically utilize an air signalpassage that is machined into the tool housing or frame.

The machining of the air signal passage in the prior art devices isexpensive and time consuming. In addition, the machining step introducessurface irregularities thus potentially creating leaks in the housing.

Therefore, it is desirable to overcome these and other limitations thusallowing overall improved performance and reduced cost of the fastenertool.

BRIEF DESCRIPTION OF THE INVENTION

Other aspects of the present invention is to provide a device of thetype describe above which is combined with other features hereafterdescribed in detail.

In accordance with one aspect of the present invention, a fastenerdriving device includes a housing containing a chamber for storingcompressed air a cylinder structure disposed within the housing, apiston movably disposed within the cylinder, a driver connected to thepiston, a main valve cooperable with the cylinder structure and movablebetween an open position and a closed position. The main valve in itsopen position allows air to move the piston through a drive stroke. Thefastener driving device also includes a trigger valve operable betweenfirst and second positions. The trigger valve in its first positioncommunicates air pressure from the chamber to the main valve through asignal passageway so as to retain the main valve in a closed position.The trigger valve in its second position allows the air to be exhaustedto atmosphere through the passageway to permit the main valve to open.The cylinder and the signal passageway comprise an integrally moldedstructure.

In another aspect of the invention, the trigger valve is operablebetween a first position wherein the trigger valve establishes a firstpressure signal at the main valve through a signal passageway so as toretain the main valve in a closed position. The trigger valve in itssecond position establishes a second pressure signal at the main valvethrough the passageway to permit the main valve to open. The cylinderand the signal passageway comprise an integrally molded structure.

In one embodiment, the structure comprising the cylinder and the signalpassageway are molded from plastic.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of the fastener tool embodying thepresent invention;

FIG. 2 is a frontal view of the cylinder of the fastener tool;

FIG. 3 is a longitudinal sectional view of the cylinder;

FIG. 4 is a top of the cylinder; and

FIG. 5 shows the map of the air path for the pneumatic signal foractuating main valve 38.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to the drawings, more particularly referring to FIG. 1,there is shown therein a fastener driving device, generally indicated at10, which embodies the principles of the present invention. Theoperation of device 10 is explained more fully in U.S. Application No.60/369,884, which is hereby incorporated by reference. The toolcomprises housing 12 having, among other things, a cylinder containingbody portion 14, a handle portion 16 and a cap portion 18. The size andshape of these components can vary considerably depending on the type offastener and application, but all have in common an internal air chamber20 for containing compressed air, for example, from an external source.

The compressed air chamber 20 is pressurized from an air supply linethrough an inlet connection attached to the handle (not shown). In thisparticular embodiment, the cap 18 may be attached to the body portion 14with screws (not shown). Part of the volume in cap 18 is used to enlargethe volume of the compressed air chamber 20. The body portion 14 and cap18 are joined by seals 22 to prevent compressed air from escaping intothe atmosphere.

The body portion 14 also includes a return air chamber 24. The returnair chamber 24 is pressurized when the piston 26 is near the end(bottom) of its downward drive stroke. The sequence of pressurizing thereturn chamber 24 will be described in detail below. The chambers 20 and24 are separated by seals 25.

The lower portion of the housing 12 is connected to a fastener carryingrail or magazine 28. The front of the rail 28 commonly is defined by anosepiece 30, which is provided with a guide cavity 32. A fastenerpusher within magazine 28 (not shown) delivers the fastener into thenose cavity 32 underneath the end of a driver 33. The driver 33 is fixedto the piston 26 and function together as a unit. A cylinder 34 ismounted in the housing 12. The piston 26 reciprocates in the cylinder 34during operation. To control the movement of the piston 26, a triggervalve 36 positioned near the handle 16 and a main valve 38 are employed.A passageway 27 permanently allows the pressure in chamber 20 tocommunicate with region 35 of main valve 38. While the main valve 38 andtrigger valve 36 can be any such valves as known in the art, it ispreferred for the main valve 38 to be made and operated in accordancewith a co-pending commonly assigned US. Patent Application entitled“Pneumatic Tool With Self-Sealing Diaphragm Valve System” Attorneydocket number 011988-0284899, Ser. No. 60/369,884, filed on Apr. 5,2002, the content of which is incorporated herein by reference.

In FIG. 1, the trigger valve 36 is positioned so as to permitpressurized air from chamber 20 to communicate through the valve 36,through signal passageway 43 and to the chamber 44 above the main valve38. The trigger valve 36 is controlled by a manual lever 40 as shown inFIG. 1. The signal passageway 43 allows air pressure signal tocommunicate between trigger valve 36 and main valve 38 through passage104, shown on FIG. 1 in dotted lines, so as to enable continuouscommunication with region 35 between first sealed portion 37 of mainvalve 38 and second sealed portion 39 of main valve 38. In thiscondition, main valve 38 is retained in a closed position due to thefact that the surface area on the valve 38 that is exposed to chamber 44is greater than the surface area of the valve 38 exposed to region 35,so that although there is equal pressure in regions 44 and 35, there isa net downward force on the main valve 38 to retain portion 39 of themain valve 38 in sealed relation to the upper end 41 of cylinder 34.Actuation of the lever 40 causes trigger valve 36 to seal the chamber 20from the signal passageway 43 and the same time opens the passageway 43to atmosphere to permit pressure in the passageways 43 and chamber 44 toexhaust through the valve 36. The passageway 43 is pressurized againwhen lever 40 is released and the valve 36 is closed. The embodiment ofthe tool shown in FIG. 1 is that of a manually operated tool, but shoulda tool be part of a stationary application the trigger valve means couldbe a remotely located valve and operated by something other than lever40. The signal passageway 43 is formed at least in major part as anintegral structure with the cylinder 34. It can be appreciated, however,that a portion of the signal passage may be considered to reside also inthe housing for trigger valve 36 or other portion of the housing 12. Aperipheral seal structure 121 surrounds an upper portion of cylinderstructure 34 and an upper portion of said signal passageway 43 tofacilitate air pressure communication of the upper portions.

A movable contact trip assembly 46 is mounted so as to have a forwardend extend outwardly of the nosepiece 30 to be actuated when the device10 is moved into operative engagement with a workpiece. The contact trip46 includes fastener depth adjusting mechanism indicated as 48 capableof being conveniently manually adjusted in a manner to determine thecountersink depth of the driven fasteners. For details of a preferredconstruction, reference may be had to a co-pending commonly assigned US.Patent Application entitled “Pneumatic Fastening Tool With FastenerDepth Adjusting Mechanism” Attorney docket number 011988-0284900, Ser.No. 60/369,882, filed on Apr. 5, 2002, the content of which isincorporated herein by reference.

The sequential operation of the above-described fastener drivingapparatus will now be described.

At rest, chamber 20 communicates through trigger valve 36, throughpassageway 43 into the chamber 44 above the main valve 38. The surfacearea of main valve 38 exposed to region 44 above the main valve isgreater than the surface area of main valve 38 exposed to region 38below the main valve. Thus, although both regions 35 and 44 are exposedto the pressure in chamber 20, the greater surface area exposed tovolume 44 causes the main valve to seal. When the trigger 40 is pulledagainst the bias of a coil spring 49, valve stem 86 is raised whencontacted by surface 51 of the trigger assembly so that the upper O-ring87 seals the air pressure chamber 20 from the signal passageway 43 andthe lower O-ring 39 is unsealed to enable the chamber 44 above the mainvalve 38 to exhaust through passageway 43 to the atmosphere throughvalve 36. Because chamber 21 is always exposed to air pressure chamber20, and because such chamber 21 communicates with the region 35, the airpressure in region 35 will cause the main valve 38 to move to itsunsealed position when the region 44 is exhausted to atmosphere. It canbe appreciated that the region 35 is disposed between the first sealedportion 37 of the main valve and the movable second sealed portion 39 ofthe main valve. The pressure in region 35 causes a rolling flexure ofportion 61 of the main valve to enable portion 39 to lift and unsealfrom the portion 41 of cylinder 34.

The opening of the main valve 38 allows the air to enter the top orfirst portion of the cylinder 34 above the piston 26. At the same time,the air communication of the upper portion of the cylinder 34 above thepiston 26 to the atmosphere through exhaust passage 50 is blocked bysealingly closing the passageway 52 in the center of main valve 38 fromthe exhaust passageway 50. Specifically, when the main valve is raisedin the open position, the upper surface of portion 90 of the main valveseals to the top member 91 of cap 18. Specifically, the upward movementof main valve 38 allows cylindrical plastic portion 90 of main valve 38to sealingly contact stop member 91 to seal passageway 52 from exhaustpath 50. The piston 26 along with driver 33 are forced downward rapidly.The driver 33 or fastener striker pushes the fastener out of the drivetrack 32 in nosepiece 30 with enough force to drive the fastener intothe workpiece.

Near the end of the drive stroke, the piston 26 passes one way checkvalves 58 in the cylinder 34 that allows air to enter and pressurizereturn air chamber 24 during the downward stroke. At the end of thedrive stroke, the underside of the piston 26 contacts a shock absorber54. After lever 40 is released, valve stem 36 is lowered under the forceof coil spring 71 so that the lower O-ring 39 seals and the upper O-ring87 unseals to permit the air pressure in chamber 20 to enter again thepassageway 43 to enable the chamber 44 above the main valve 38 to bepressurized again through passageway 43. Therefore, the air pressure inthe chamber 44 above main valve 38 is equalized with the air pressure inchamber 21 which is always exposed to air pressure chamber 20 (throughpassageway 45). The surface area of main valve 38 exposed to region 44above the main valve is greater than the surface area of main valve 38exposed to region 35 below the main valve. Thus, although both regions35 and 44 are exposed to the pressure in chamber 20, the greater surfacearea exposed to volume 44 causes the main valve to go back to itsinitial sealed position. The main valve 38 is pneumatically balancedtowards the closed position whenever both the upper and lower sides aresubjected to equal air pressure. The main valve 38 thus closes whencavity 44 is pressurized.

It should be appreciated that the principles of the present inventionapply to what are known in the art as half-cycle valving systems, fullcycle valving systems, and automatic cycle valving systems.

The shifting of the main valve 38 to the closed position unseals thesealing engagement between the plastic portion 90 of main valve 38 andthe stop member 91 so as to allow the space above the piston 26 duringupward travel of the piston 26 to exhaust through passageway 52 andexhaust passage 50 to atmosphere. The air above the piston 26 exhaustssequentially through canal 89, passageway 50 and an exhaust port (notshown). When the air pressure above the piston 26 drops below that underthe piston 26, the air in the return air chamber 24 enters the cylinder34 under the piston 26 through canal 59 and forces the piston 26 anddriver 33 upward. Return air chamber 24 has a fixed volume, thus aspiston 26 moves upward the pressure in return air chamber 24 is reduced.

The return air chamber 24 is designed with sufficient volume to provideenough air to fully return the piston 26 at the lowest operatingpressure with the pressure being reduced to nearly that of theatmosphere prior to the next tool cycle. As the end of the driver 33raises above the fastener rail 28, the next fastener is positioned intothe guide cavity 32 ready to be driven by the next tool cycle.

Turning now to FIG. 2, a frontal view of integrally cast structure 62,comprising the cylinder 34 and air passage 43, is shown. In oneembodiment, structure 62 is molded from a molten polymeric material suchas plastic in a mold structure. In another embodiment, structure 62 ismolded from a molten metal material in a mold structure. The moldstructure (not shown) is used to form the shape of structure 62. Themold structure defines both the cylinder 34 and the air passage 43. Thestructure 62 comprises integrally cast exhaust passage or air canal 43communicating a volume of air above valve 38 with a trigger valve 36.Structure 62 is held inside body portion 14 of housing 12 (shown inFIG. 1) with sealing mount 60.

FIG. 3 is a longitudinal cross-section of structure 62 in the line 3-3in FIG. 2. Again in this Figure is shown air canal 43. In addition, aircanal 43 continues through an angular path leading to trigger valve 36.FIG. 4 is a transversal view of top of cylinder 34 showing clearly theair canal 43 in relation with the piston 26 in cylinder 34. Referringback to FIG. 3, structure 62 comprises cylindrical portion or cylinder34. Specifically, the cylindrical portion or cylinder 34 has an innercylindrical surface 110 adapted to cooperate with piston 26 (shown inFIG. 1). The cylindrical portion 34 has a longitudinal axis AA. Thepassage portion or air canal 43 is disposed radially outwardly from theinner cylindrical surface 110. The passage portion 43 has an upperportion 111 adapted to communicate with an upper portion 112 of thecylindrical portion 34. The passage portion 43 further has a lowerportion 113 adapted to communicate with the trigger valve 36 (shown inFIG. 1). The peripheral seal structure 121 is also shown surrounding theupper portion 112 of cylinder structure 34 and the upper portion 111 ofthe signal passage 43.

FIG. 5 shows the map of the air path 80 for actuating valve 38. Thevalve 38 remains against the cylinder 34 as long as both sides of valve38 are subjected to equal air pressure. To fire the tool, the upper sideof the valve 38, positioned opposite to cylinder 34, must be subjectedto reduced pressure. This is done by exhausting cavity 44 throughexhaust passageway 43 by actuating the trigger valve 36 as illustratedin FIG. 5. Now that the opposite sides of the valve 38 are subjected tounequal pressure, the valve 38 is forced to deflect upward thus thelower portion of valve 38 retracts from cylinder 34. Movement of theflexible valve 38 away from the top of cylinder 34 allows pressurizedair to enter and force the piston 26 downward.

As previously described, during the tool cycle in which the piston 26returns to the uppermost portion of the cylinder 34, the air above thepiston 26 must be exhausted to the atmosphere. The compressed air usedto drive the piston 26 downward can exhaust to the atmosphere by goingthrough exhaust passageway 50 and out of exhaust port.

It should be appreciated that the integrally formed cylindricalstructure 34 and signal passageway 43 can be used in any pneumaticfastening tool that requires such portions and is not limited to use inconjunction with the particular components employed in the preferredembodiment.

It must be understood the terms such as upper, lower, above, downwardand the like are used in reference to the figures shown in the drawingssolely for the purpose of clarity. While the preferred embodiment of thepresent invention has been shown, it is anticipated those skilled in theart may make numerous changes and modifications without departing fromthe spirit of this invention which is intended to be limited only by thescope of the following appended claims.

While the invention has been described in connection with particularembodiments, it is to be understood that the invention is not limited toonly the embodiments described, but on the contrary it is intended tocover all modifications and arrangements included within the spirit andscope of the invention as defined by the claims, which follow.

1. An integrally molded structure for use in a fastener driving devicecomprising: a cylindrical portion having an inner cylindrical surfaceadapted to cooperate with a piston, said cylindrical portion having alongitudinal axis, a passage portion disposed radially outwardly fromsaid cylindrical surface and having an upper portion adapted tocommunicate with an upper portion of said cylindrical portion and alower portion adapted to communicate with a trigger valve, said passageportion being integrally molded with said cylindrical portion.
 2. Amethod of forming a cylindrical structure and a signal passageway for afastener driving device comprising: providing a mold structure thatdefines both said cylindrical structure and said signal passageway;introducing molten material to said mold structure; and forming bothsaid cylindrical structure and said signal passageway in a moldingoperation.
 3. The method of forming a cylindrical structure and a signalpassageway as recited in claim 2, wherein said material comprises apolymeric material.
 4. The method of forming a cylindrical structure anda signal passageway as recited in claim 2, wherein said materialcomprises a metal.